c l i n i c a l f o l i o s : d i s c u s s i o n



Breast Imaging Update

 

 

Related narrative: Axillary Recurrence of Breast Cancer

The standard breast imaging techniques of mammography, ultrasound and MRI are rapidly being enhanced and supplemented with new modalities. Where the standard techniques provide structural information about breast lesions, the evolving technologies are providing dynamic functional data which can more accurately characterize breast lesions.

Enhancements of standard techniques include digital mammography, which has proved superior for dense breast tissue, for digital manipulation, storage and transmission. Ultrasound is effective for dense breast tissue, to characterize indeterminate palpable and mammographic lesions, to evaluate axillary lymph nodes and to guide minimally invasive biopsy.

It was hoped that MRI coupled with diffusion weighted imaging (DWI) could better characterize lesions and helps compensate for the high sensitivity and decreased specificity (high false positives) of MRI, but this approach has been disappointing because it requires homogeneous fat suppression for good images.

New modalities include computer-aided diagnosis, single photon emission planar CT (SPECT), positron-emission tomography (PET), PET-CT hybrid, and radionuclide scintigraphy (sestamibi, peptide, immune-). In the past ten years, fluorodeoxyglucose (FDG) PET has become a useful tool in specific circumstances. FDG-PET/MRI-DWI may also become available in the near future.

The common breast cancers have increased vascularity which correlates with their increased metabolic activity. FDG uptake reflects this elevated metabolism, but like most radionuclide imaging techniques yields poor structural resolution. Multi-detector high resolution CT (MDCT) gives enhanced structural resolution. Adding contrast and a dynamic component to the scan (DCECT) reflects tumor angiogenesis, perfusion and vascular permeability. Combining the two techniques (FDG-PET/DCECT) provides a powerful tool to evaluate the functional status of a lesion.

A major benefit of this fusion is the ability to do rapid whole body scans for staging purposes, to assess the response to neoadjuvant therapy, to differentiate scar tissue from metastatic/recurrent disease, and to detect and follow metastatic disease. The technique is not useful for screening and early detection due to the decreased sensitivity for smaller lesions (53% for lesions <5mm) and slow-growing lesions with reduced metabolism and perfusion. Recent surgery, chemo and radiotherapy can cause increased perfusion and raise the false positive rate.

Reference:

Das CJ et al; FDG-PET Dynamic Contrast Enhanced CT in the Management of Breast Cancer. PET Clin 4(2009), 255-263.


This page was last modified on 5-Mar-2010.